On the rule of mixtures for bimetal composites

In the present study, mechanical behavior of bimetal composite rods was systematically studied by tensile and compressive tests on three types of bimetal rods, Al 6082/Al 7050, Mg AZ31/Mg ZK60 and Mg AZ31/Al 7050 and compared with the rule of mixtures (ROM) predictions. The influence of the interface characteristic (i.e. the diffusion layer) and the strain hardening behavior of two components on the ROM was addressed. Our results show that when the two components have a similar work hardening behavior, the ROM for flow curves is applicable irrespective of the interface characteristic. When there is a large mismatch in strain hardening, the efficiency of ROM is highly dependent on the thickness of diffusion layer. With a diffusion layer about 10 µm thick, the ROM calculation is in good agreement with the experimental one. In contrast, the experimental flow curve would largely deviate from the ROM calculation with a diffusion layer about 300 µm thick. The corresponding causes are related to cracks on the interface and load transfer. It is also found that the ROM for yield strength can work well in all bimetal composite rods.